A present arrangement in customer telephone station equipment includes a modular jack at a wall outlet and in a base of a telephone set. The telephone set is connected to the wall outlet through a line cord by inserting modular plugs at the ends of the line cord into the jacks. A customer may wish to place a telephone set at a particular location, but a wall outlet may not be near enough to permit connection with the initially provided line cord. Customers are able to relocate their telephone sets by using customized lengths of line cords joined together by couplers to extend from the sets to wall outlets.
While customer combinations of cords satisfies the desire for convenience and portability, it can lead to a problem. As is well known, most telephone cords are made by helically wrapping a plurality of tinsel ribbons about a center core and then insulating the ribbons. If the loop length from the wall outlet to the telephone and return is too lengthy, transmission characteristics will be affected because of excessive resistance. It has been recommended that the customer use cordage comprising stranded conductors, which has a lower resistance than tinsel conductor cordage, to extend the standard length line cord that is generally supplied with the telephone set.
The foregoing problem has been overcome by a cord of a system which includes a coupler having a disconnection encumberance. The coupler includes a unipartite housing which is made of a dielectric material. The housing has an externally communicating plug-receiving cavity at each end and a plurality of spaced passageways that extend from one end to the other. A contact element in the form of a wire having a linear portion is received in each passageway. Each end portion of each wire is formed into a retroflexed configuration. The externally communicating cavity at each end of the coupler is adapted to receive a modular plug having blade-like terminals which engage aligned ones of the retroflexed portions of the contact elements when the plug is inserted into one of the cavities. A modular plug at one end of a stranded conductor line cord of a desired length is inserted into a particular one of the coupler cavities. When a modular plug is inserted into that cavity, the modular plug, including a resilient locking tab, is disposed completely within the housing to preclude digital depression of the tab and withdrawal by a customer. This prevents inadvertent customer connection of excessive lengths of high resistance tinsel type cordage which could have adverse effects on the transmission characteristics of the customer loop.
If a wall outlet jack is positioned so that an existing line cord to a proposed telephone set location is of insufficient length, the telephone set is disconnected by removing the modular plug of the line cord from the wall jack. The disconnected plug of the line cord is inserted into the unused one of the two opposed cavities of the coupler at its so-called customer end. The uncoupled end of the stranded conductor line cord is inserted into the jack in the wall outlet. On the other hand, if the telephone set has been positioned at a location extremely remote from a wall outlet by the use of a tinsel line cord in combination with a stranded cord, it may be desired to move the set closer to the outlet. The stranded conductor line cord is easily disconnected by removing the uncoupled end of that line cord from the wall outlet and unplugging the end of the original line cord from the coupler jack and inserting it into the wall outlet.
Methods and apparatus are required for forming the contact elements within the one piece plastic housing. End portions of each contact element must be formed so that they are adapted to engage terminals of modular plugs which are inserted into the cavities at the ends of the coupler. Because it is expected that modular plugs will be moved into and out of the cavity at the customer end to permit telephone rearrangements, the end portions of the contact elements at the customer end must have a predetermined retroflexed configuration. This will ensure suitable contact with the terminals of a modular plug upon each insertion.
Another problem has arisen because of the relative sizes of the wires and of the passageways of the housing. It has been found that the passageways in the housing must be sized larger than the cross-section of the wire-like contact elements. Otherwise core pins which are used during the injection molding of the housing and which are moved into a mold from opposite ends are too flexible and are deflected out of alignment with each other during the molding. The oversizing of the passageways of the housing causes a problem when attempting to form the retroflexed end portions of the wires which are disposed in the one piece housing. Inasmuch as the cross-section of each wire is substantially smaller than the cross-section of each passageway, it will bow along its center portion when the end portions of the wires are being formed.
Seemingly, the prior art is devoid of methods and apparatus that meet these needs. What is needed are methods that are capable of implementation in a manual or automatic manner to load lengths of resilient metallic wires into a unipartite coupler housing and to form them into contact elements, the ends of which have a predetermined configuration.